The present invention relates to a dual roll type continuous casting machine capable of effectively preventing the so-called triple-point problem.
As shown in FIG. 1, a dual roll type continuous casting machine has a pair of cooling rolls 1 in parallel with each other and spaced apart from each other by a suitable distance as shown in FIG. 1. Side seal plates 2 are disposed at the ends of the cooling rolls 1 to define a molten bath or pool (in some cases, barrel seal plates are disposed, extending in the axial direction of the cooling rolls 1). Molten metal is poured into the molten bath and is cooled by the cooling rolls 1 which are rotated in the directions indicated by the arrows so that a cast piece 3 continuously emerges out of a roll gap between the rolls 1.
Solidified shells are developed over the surfaces of the cooling rolls 1 as the molten metal in the molten bath is cooled by the cooling rolls 1. Abnormal growth of the solidified shells is observed at the so-called triple points (i.e., the points of contact between the cooling roll 1, the side seal plate 2 and the molten metal since the molten metal tends to tarry and thus tends to be sooner cooled at the triple points. The abnormally grown solidified shells are pulled by the solidified shells developed on the cooling rolls 1 and drops (separated) into the gap between the cooling rolls 1. As a result, not only the surfaces of the cast piece may be degraded, but also the thickness of the cast piece may be increased locally, causing breakdown of the same. In addition, drop of the abnormally grown solidified shells may cause damages on the side seal plates 2.
To overcome such triple problem, it has been devised and demonstrated to pour the molten metal 5 into a core 4 disposed in the molten bath and is caused to flow through holes 6 on the core 4 into the gap between the cooling rolls 1 in a fluidized state for prevention of the abnormal growth of the solidified shells at the triple points.
However, even the above-described system cannot satisfactorily overcome in practice the triple-point problem because it is impossible to effectively melt only the harmful solidified shells grown at the triple points. More specifically, when the molten metal is directed to flow directly toward the triple points, not only the solidified shells at the triple points but also the solidified shells on the cooling rolls are melted.
In view of the above, according to the present invention, of the solidified shells grown at the triple points, only the solidified shell which are harmful and are grown at the side seal plate is effectively melted away.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.